1. Field of the Invention
The present invention relates to a cutter head for a tunnel excavator which is improved in frame construction.
2. Prior Art
A prior art tunnel excavator for tunneling comprises a cutter head rotatably provided in front of a shield body for excavating the working face of a tunnel.
Particularly a tunnel excavator for excavating a rock bed comprises a cutter head equipped with a plurality of disk cutters rotatably attached to the front surface thereof for excavating the rock bed, but they are worn away after excavating a long distance to lower the efficiency of excavation.
Accordingly, various ideas are proposed to facilitate the exchange of the worn-out disk cutters from inside the cutter head.
For example, there is proposed in the Japanese Patent Publication No. 1 - 38959 a cutter head comprising a central hub provided in the central portion thereof and a plurality of spokes which radially project from the central hub, wherein disk cutters can be attached to or detached from the central hub and the spokes from inside the cutter head.
The prior art cutter head described above, however, has such drawbacks in that it requires numerous steps for accurately positioning the central hub in the central portion of the cutter head in manufacturing the same which employs a frame construction of supporting the central hub provided in the central portion thereof by a plurality of radially projecting spokes so that it is not so easily assembled and moreover if the central hub is not accurately positioned therein, an abnormal load is applied to the disk cutters attached to the central hub so that the life thereof is shortened.
The present invention has been made in view of the conventional drawbacks to provide a cutter head for a tunnel excavator having a strong and easily manufacturable frame construction.